a. Field of the Invention
The present invention relates generally to portable electrical mixers, and, more particularly, to a hand-held wand mixer for mixing, chopping, blending, and general processing of food items and similar materials.
b. Background Art
In the commercial food service industry, as well as certain other fields such as the chemical and pharmaceutical industries, it is common to utilize comparatively large, hand-held electric mixers for the bulk preparation of food items and other products. Examples of such food items include various batters, soups, salads, and so on. Such mixers are generally used in combination with a large bowl or other mixing vessel in which the food items or other materials are combined. A variety of attachments and tools are employed, such as chopper blades, whisks, kneading tools or comminuting rods, to mix, blend, whip, chop or emulsify the food or other material to the desired consistency.
A particular class of such mixers is commonly referred to as “wand mixers”. Wand mixers typically include an electric motor enclosed within a housing at the upper end of the mixer, and an elongate “wand” portion that encloses the drive shaft leading to the mixing attachment. In operation, the motor housing is usually held in one of the operator's hands while the elongate wand portion is gripped in the other, so that the operator is able to exert the control and leverage necessary to move the tool through the mixture.
The drive shaft is coupled to the rotating motor shaft and extends downwardly a substantial length (e.g., 12-18 inches) iii order to provide reach for the processing tool that is mounted to its lower end. The elongate wand portion typically has a tubular configuration and usually includes a bearing at its lower end for lateral support of the drive shaft, the upper end of the drive shaft being supported by its attachment to the output end of the motor shaft. In addition, the tubular housing normally supports a protective blade guard at its lower end, typically an open ended, somewhat bell shaped cup which encompasses the chopper blade but includes lateral openings that allow the mixture to flow to and from the chopper blades or other mixing tool. The primary function of the blade guard is to protect the user and food containment vessel from the rotating blades, and it also reduces splashing during the processing of low viscosity foods
The mixing process is inherently messy, and the processing tool, blade guard and tubular housing invariably become covered with particulate food or other residue. In addition, the rapidly rotating tool or blade often acts somewhat like a pump, generating upward flow that tends to force residue into the tubular housing where the drive shaft emerges. Because the drive shaft bearing and other moving parts reside within the housing, any influx of contaminate material may degrade the integrity of these components. Furthermore, any food residue that evades the cleansing process can quickly become a source of bacterial contamination, posing potentially serious health consequences.
Consequently, many efforts in the prior art have focused on improving the hygienic and sanitary aspects of such mixers. In some instances, these have taken the form of modular assemblies that can be dismantled for cleaning. Such designs generally accept the notion that debris and fluids will enter the tubular housing and thus require disassembly for cleaning. In one example, a removable drive shaft bearing is used so as to allow the drive shaft and other internal components to be withdrawn from the housing tube for cleaning, and in another example, the tubular housing is configured in two portions that detach and break down to provide access to their internal components. While such approaches may help ensure that the mixer is safely sanitized, the disassembly and re-assembly that is required is both tedious and time consuming. In addition, such assemblies tend to be complex and expensive to produce.
Other devices have taken the approach of improving the sealing mechanism at the bottom of the mixer wand, in an effort to prevent debris and fluids from entering the tubular housing to begin with. While some of these designs may reduce the amount of seepage entering the tubular wand during operation of the mixer, their general design is such that the sealing mechanism is rendered ineffective during actual cleaning of the assembly. For instance, due to the weight and bulk of the motor assembly, plus the fact that most motor housings are not intended to be fully immersible, it is generally required that the drive shaft and its tubular housing be removed from the motor for cleaning. However, the spatial relationship of the drive shaft within the tubular housing generally relies on the motor shaft bearing and the bearing at the lower end of the wand. Thus, when the drive shaft and its housing are detached from the motor assembly, the free end of the drive shaft (which was previously coupled to the motor shaft) is released from its fixed spatial relationship with the tubular housing and tends to bend or pivot within the housing as the assembly is cleaned, inevitably causing deformation of the seal at the opposite end. Water and debris then enter the tubular housing through the deformed seal and contaminate the internal components.
Yet another deficiency of this configuration is that the lateral loads imparted to the upper end of the drive shaft during operation of the mixer must be reacted by the motor bearing alone. The added loading results in increased motor wear, thus reducing motor longevity and increasing maintenance requirements.
Accordingly, there exists a need for hand-held wand mixer that can be thoroughly cleaned and sanitized without requiring disassembly of the wand portion of the mixer. Furthermore, there exists a need for such a mixer having an improved sealing mechanism which ensures that both debris and fluids cannot contaminate or degrade the internal components of the shaft assembly, even during cleaning. Still further, there exists a need for such a mixer that provides increased motor longevity and reduced maintenance. Still further, there exists a need for such a mixer having a construction that allows convenient disassembly when actual maintenance or repair is required. Still further, there exists a need for such a mixer that avoids excess complexity and is economical to produce.